In Croatia, Grubelnik families are Croats (from Sisak ).
Prevalence
About 10 people with faimily name Grubelnik live in Croatia today, in one household only. There were 0 of them in the middle of the past century, and their number multiplied. They are located in one Croatian city only, in Sisak (<5).
In the sources analysed in the project Acta Croatica so far, the name is mentioned over twenty times, the first time 1906 in source Yearbook and Directory of Literary Society of St. Jerome 1906.